For systems that require ultra high frequency (UHF) and GPS communications, generally separate GPS antennas and UHF communication antennas are needed. Using two separate antennas in these cases is not a cost effective use of space on any platform. Particularly, small unmanned ground vehicles (SUGV), unmanned aerial vehicles, micro unmanned aerial vehicles, and soldier back pack applications are systems where antenna space is limited and antenna placement is important. A need therefore exists for an antenna design that minimizes antenna space on systems without impacting antenna performance.
More particularly robot vehicles have a requirement to communicate with base stations using UHF band communications. These vehicles also need to report back to the base station their exact location. While it might be thought that GPS L band antennas could be used both for geophysical location and communications, the L band antennas do not work for communications purposes especially in the UHF band. There is therefore a need for a low profile efficient dipole antenna that has its center some distance above the ground for propagation purposes while at the same time supporting GPS functionality.
In addition to the robot applications and applications involving the signaling of position of mobile devices such as remotely controlled vehicles and the like, as well as communicating with these devices, there is also a need for providing precise GPS timing signals to a class of transceivers termed Joint Tactical Radio System (JTRS) radios. In these applications it is not so much the requirement to be able to receive GPS signals for geo-location purposes, rather it is the functionality of such JTRS radios which are in essence software-defined radios. In order for software-defined radios to operate one has to have precise timing signals. This timing is provided in one embodiment through the detection of GPS timing signals both in the L1 and L2 bands, with the timing signals being especially important for the cyber encryption/decryption systems that are utilized with these radios.
Regardless, what is required is a low profile antenna to replace the monopoles in the form of rubber duck types of antennas with an increased gain UHF bands antenna as well as to provide extra height for the antenna. Additionally for JTRS radios they are often times located in backpacks. It is thus important to provide a low profile antenna that has been optimized for use with the new JTRS radios as well as providing these radios with GPS waveform timing signals.
It is noted that the two timing signals that are available from the L1 and L2 bands are required for the precision timing, specifically for crypto applications. In fact, many of the software-defined radios of the JTRS variety are architected to time their waveforms with timing signals from the L1 and L2 bands GPS signals.
There is therefore a necessity to provide a combined UHF/GPS antenna with a stiff but spring loaded housing and to provide the antenna with good UHF propagation characteristics to achieve ranges unattainable by rubber duck type antennas. It is also important to be able to provide the antenna with a sufficient flexibility so that if it contacts a stationary object, the vehicle to which it is mounted is not overturned or alternatively that the antenna is not itself damaged.
In terms of the operating range for such an antenna it would be desirable to have an operating range between 225 MHz and 400 MHz for the UHF antenna, with the two GPS antennas operating in the gigahertz L1 and L2 bands.